/*
 * Copyright 2019 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "sensors/median_filter.h"

#include <algorithm>
#include <vector>

#include "util/vector.h"
#include "util/vectorutils.h"

namespace cardboard {

MedianFilter::MedianFilter(size_t filter_size) : filter_size_(filter_size) {}

void MedianFilter::AddSample(const Vector3& sample) {
  buffer_.push_back(sample);
  norms_.push_back(Length(sample));
  if (buffer_.size() > filter_size_) {
    buffer_.pop_front();
    norms_.pop_front();
  }
}

bool MedianFilter::IsValid() const { return buffer_.size() == filter_size_; }

Vector3 MedianFilter::GetFilteredData() const {
  std::vector<float> norms(norms_.begin(), norms_.end());

  // Get median of value of the norms.
  std::nth_element(norms.begin(), norms.begin() + filter_size_ / 2,
                   norms.end());
  const float median_norm = norms[filter_size_ / 2];

  // Get median value based on their norm.
  auto median_it = buffer_.begin();
  for (const auto norm : norms_) {
    if (norm == median_norm) {
      break;
    }
    ++median_it;
  }

  return *median_it;
}

void MedianFilter::Reset() {
  buffer_.clear();
  norms_.clear();
}

}  // namespace cardboard
